I'm hoping these will be good suggestions but then again they might only be good to me. (If that makes any sense.)

In Guilds the Ranks are; Recruit, Member, Veteran, Officer and Guild Master.
Officers have the power to invite members, remove members, promote and demote players. Veterans, they have no powers. I am suggesting that Veterans have the power to invite members to the guild.

I also think that Guild Masters should be able to decide whether or not certain Veterans/Officers should have certain powers. By that I mean when you are leader of a level you can choose to invite friends, guild mates or no-one at all. I think you should have options for Veterans/Officers. To allow them to have certain powers or none at all.

My other suggestion is Friend chat or /f chat. We're able to talk to our Guild to ask for help but if we need to ask a friend you have to /tell and sometimes you just dont have the time. So if you say /f Anyone for (level)? I think that would work quite well :)